Similar compounds are described in WO 91/02709 and WO 91/08184. However, the novel compounds are not mentioned therein.
The substances employed hitherto for this purpose all have certain disadvantages, for example excessively high melting points, excessively low clearing points, inadequate stability to the presence of heat, light or electric fields, inadequate electrical resistance, an excessively high temperature dependence of the threshold voltage, or unfavorable dielectric and/or elastic properties.